Some hybrid vehicles may include a driveline disconnect clutch that can mechanically isolate one portion of a driveline from a second portion of the driveline. For example, an engine may be selectively isolated from a transmission and vehicle wheels via a driveline disconnect clutch so that the transmission and wheels may operate independently from the engine. The driveline disconnect clutch allows torque to be provided to the driveline to propel the vehicle even if the engine has stopped rotating. However, during conditions where a desired demand or driveline torque is higher, the driveline disconnect clutch may be closed to provide the desired demand torque. Closing the driveline disconnect clutch may induce a torque disturbance into the driveline if the driveline disconnect clutch transfers more torque than is desired. In particular, closing a driveline disconnect clutch during engine starting may induce a driveline torque disturbance that is noticeable to a driver. Thus, a driveline that includes a disconnect clutch may be useful to improve vehicle fuel economy, but the increased fuel economy may come at the expense of increased driveline noise vibration and harshness (NVH).
The inventors herein have recognized the above-mentioned disadvantages and have developed a method of operating a hybrid vehicle driveline, comprising: opening a closed torque converter clutch in response to an engine start request; and adjusting a driveline integrated starter/generator (DISG) speed in response to a desired torque converter impeller speed.
By opening a torque converter clutch in response to an engine start it may be possible to reduce a driveline torque disturbance caused by closing a driveline disconnect clutch. Additionally, speed of a DISG may be adjusted so as to control the amount of torque that is transferred through a torque converter so that driveline torque pulsations may be reduced before being transmitted to vehicle wheels via a transmission.
The present description may provide several advantages. Specifically, the approach may reduce driveline torque disturbances of a hybrid driveline. Further, the approach may improve vehicle drivability. Further still, the approach may reduce driveline wear, thereby increasing the operating life of the driveline.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.